Method of and apparatus for molding pulp articles



Dec. 24, 1935. R. D. HEYMANN ET AL 2,025,053

METHOD OF AND APPARATUS FOR MOLDING PULP ARTICLES Filed May 26, 1933 mmmm Patented .Dec. 24, 1935 UNITED" STATES PATENT OFFICE METHOD OF AND APPARATUS FOR MOLDING PULP ARTICLES tion of Delaware Application May 26, 1933, Serial No. 672,918

4 Claims.

This invention relates to theart of molding hollow articles of paper pulp, and more particularly to articles which have a relatively small opening and which may have irregular shapes.

In molding articles by flowing dilute paper pulp stock into a hollow screen mold, difficulty has been experienced in obtaining substantial uniformity in wall thickness. In the making of certain articles such as toy figures, the presence of comparatively thin wall portions may not be open to serious objection, but, where such articles as containers intended for liquids are made, it is highly important that the wall thickness be substantially uniform throughout so as to avoid the presence of weak areas subject to rupture. Fur thermore, in'special articles such as milk bottles which must be shaped to provide a suitable seat for the customary disk cap, difiiculty has been heretofore experienced in molding such abottle with a sufilciently strong seat to receive and hold the cap securely. Apparatus embodying the present invention overcomes this dimculty and makes it possible to manufacture milk bottles of conventional shape having suitable seats for the caps.

According to the invention, a suitable mold is provided for the molding of articles as desired, the dilute pulp stock being introduced into the mold through a suitable nozzle which is preferably constricted atits discharge orifice so as to increase the velocity of the pulp stream as it enters the mold. This nozzle preferably projects downwardly into the interior of the mold a substantial distance toward the bottom thereof. The exterior diameter of the end portion of the nozzle may also be made as large as possible for the purposes hereinatfer set forth.

In molding special shapes such as bottles of conventional shape having necks which are relatively narrow as compared with the bodies of the bottles, special structurehas been provided, according to the invention, to insure suflicient wall thickness at the upper or neck portion of the bottle. Other improved features of structure and operation will be apparent to one'skilled in the art from the description of the invention which follows and from the drawing in which Figure 1 is a sectional view of molding apparatus including an embodiment of the invention.

Figure 2 is a diagrammatic sectional view of similar apparatus slightly modified.

Figure 3 is a view similar to Figure 2 showing another modification.

Figure 4 is a portion of Figure 1 shown on a larger scale.

Figure 5 is a fragmentary sectional view of molding apparatus for an article of another shape,

this being shown on a larger scale.

Figure 6 is a conventional sectional view of a diiferent shape of mold and nozzle for the same. 5 Figure 1 illustrates portions'of an apparatus for molding hollow pulp articles, such apparatus including a suitably supported member II! from which swingably depend a number of mold sup: ports ll each of these supports having a section 10 I2 of a mold. Suitable apparatus, a portion of which is indicated at I3, is provided to swing the members ll together to form a complete mold, and to swing them outwardly to discharge a molded article. The moldsections l2 are each lined with a suitable screen If), which may be of woven wire, perforated sheet metal, or any other equivalent structure. A bottom member l6 may be provided to cooperate with the lateral members l2 so as to complete the shape of the mold, this member It being adapted to be moved downwardly when the members 15 are swung apart for the discharge of the molded article. Through the member Ill a supply pipe 20 projects from a suitable vat or tank 2| diagrammatically indicated in Figures 2 and 3. The supply pipe 20 maybe provided with a valve 22 of any suitable structure to shut olf the supply of pulp when desired. An auxiliary pipe 25 may lead into the pipe 20 below the valve 22 for the introduction of compressed hot or cold air, steam, or other fluid into the pipe 20, a valve. 26 being'pro'vided in the pipe 25 to control the fluid therein. The screen mold l5, shown in Figures 1 to 4, has, by way of example, the shape of a conventional cylindrical bottle with a neck portion of considerably smaller diameter than the body portion. For molding of pulp bottles of this and similar shapes, a supply nozzle 30 projects downwardly from the supply pipe 2|! a sufficient distance to extend well toward the bottom of the screen mold Hi. The external diameter of this nozzle is necessarily limited to a size equal to the inner diameter of the mouth of the bottle to be molded since the nozzle must be retracted from each molded bottle after it has been formed. In order to avoid as far as possible retardation of flow of pulp stock from the supply tank, a supply pipe 20 of substantial interior diameter is preferably employed. Since for molding of a narrow necked bottle a nozzle of relatively small diameter must be employed, the necessary reduction in diameter from the pipe 20 to the nozzle 30 is preferably made by one or more internal tapers as at 3| and 32 so that no sharp shoulders are provided to form eddy currents in v the pulp stream, to retard the flow or to afford lodgment for masses of pulp fiber.

In the molding of bottles or other figures with comparatively narrow portions, the nozzle must not only be small enough to be withdrawn from the mouth of the molded article, but sufiicient clearance must be provided between the neck portion of the mold and the adjacent wall of the nozzle so that there can be free access of pulp stock to the uppermost end of the interior of the mold for the deposition of pulp at the uoper end or mouth of the molded article. On me other hand, where the body portion of the molded article is of substantially greater diameter than the neck portion, it is preferred to employ a nozzle having its lower portion of maximum diameter so as to reduce as far as possible the clearance between the lower portion of the nozzle and the adjacent portions of the mold. To this end, the lower portion of the nozzle 30 may be formed with a thickened wall so that the exterior diameter of this portion of the nozzle is as large as possible consistent with the removal of the nozzle through the mouth of the molded article. Instead of thickening the wall as at 35, the wall may be spun outwardly as illustrated at 36 in Figure 3 so as to provide a maximum exterior diameter for the portion of the nozzle opposite the body portion of the mold l5. At the lower end of the nozzle 30, the bore thereof is constricted as at 31 to form a reduced orifice 38. This feature, combined with the use of a supply pipe 20 of substantial size, makes possible the projection of the pulp stream through the orifice 38 with a considerable velocity without excessive pressure hehind it, since the resistance to the flow of the pulp through the supply pipe nozzle, due to fluid friction, is reduced to a minimum by the provision of the pipe 20 of large size.

In molding a pulp article with the apparatus thus far described, a dilute aqueous suspension of paper pulp is supplied at suitable pressure from the tank 2| through the nozzle 30, the constricted orifice 38 resulting in the entrance of the stock into the mold in a stream having considerable velocity. The mold is quickly filled with stock and is maintained completely filled for a period of a few seconds, during which time white water escapes through the screen and through the pulp mat which is thereby formed on the inner surface of the screen. When a sufiicient interval of time has elapsed for the deposition of a pulp layer of suitable thickness, the valve 22 is closed and the valve 26 is immediately opened for the introduction of compressed air, steam, or other gas or vapor through the nozzle 30. The reduced orifice 38 increases the velocity of the air stream which enters the body of pulp stock still remaining in the mold. The air jet instantly drives the body of aqueous pulp up into the upper portion of the mold. The pressure of the air, which may be of the order of 60 pounds or so at the gage, quickly drives out the white water of the residual stock through the screen mold. The sweeping action of the air which elevates the residual stock to the upper portion of the mold is augmented by the enlarged external diameter of the lower portion 35 or 36 of the nozzle 30, his enlargement of the nozzle decreasing the clearance between the surface of the mold so as to increase the velocity of the upward flow of the stock. As a result of this structure, the last of the pulp stock is swept more efiiciently to the uppermost portions of the mold so that the molded article has a wall thickness which is substantially uniform to its upper end. Thus the molding of the bottles with comparatively thin walls at their upper portions is avoided.

"In addition to the difiiculty of thin walls at 5 the neck portions of the bottle-shaped molded containers, further difilculty has been experienced in the past in providing uniformity of wall thickness immediately adjacent to the mouth of the molded bottle. For some reason not wholly under- 10 stood but probably due to local-eddy currents, molded bottle-shaped containers have been subject to local thin spots in the wall of the neck near the mouth of the container; This difiiculty' is overcome by the provision of a suitable collar 40 15 of tapered thickness surrounding the nozzle 30 at the point where the nozzle passes into the mouth of the mold. The degree of taper of the collar 40 is determined experimentally, but it is found that such a collar, if suitably tapered, results in the 20 depositing of the pulp in such a manner thatthe wall portions adjacent to the mouth of the container are of unifonn thickness substantially equal to that or the rest of the molded article. In Figure 5 acollar 4| is provided, the taper of 25 which difiFers from that of the collar 40. The collar 4| is employed in the molding of containers having the shape of a conventional milk bottle with a rounded lip portion 42 and an inward flange 43 adapted to provide a seat for a disk bot- 30 tle cap. The collar 4| ensures the molding of a flange 43 with a thickness substantially equal to that of the wall of the container, instead of a thin fin or feather which has characterized earlier attempts to mold a container of this shape without 85 the use of a member such as the collar 4|.

Figure 6 is a conventional showing of a screen mold 45 of special shape, together with a suitable nozzle 46 for the introduction of pulp stock into the mold. This nozzle has a constricted passage 40 41 near its lower end to introduce the stock and air at relatively high velocity for the purposes hereinbefore set forth. The lower tip of the nozzle may be internally flared as at 48 so as to permit the stream of stock to spread as it enters 45 the mold so as to distribute the pulp more evenly on the surface of a screen mold having a shape of the type illustrated in Figure 6.

It will be observed that a characteristic feature of our invention, as shown in the various forms 50 disclosed, includes the introduction of the pulp and compressed air through the reduced neck portion of the mold and through a duct having a restricted discharge orifice located within the mold at a point sufiiciently removed from the 5 neck entrance to insure the uniform distribution of the pulp through the mold.

It is evident that the specific shapes and dimensions of the parts herein described and illustrated are subject to alteration to adapt them to the molding of various articles of special shape. The specific examples herein described and illustrated are given not by way of limitation but by way of illustration and are subject to such modification and changes as fall within the scope of the invention as set forth in the following claims.

We claim:

1. Molding apparatus for hollow pulp articles,

comprising a hollow screen mold having an opening or mouth therein, a supply nozzle projecting 0 through said opening into said mold, a ring on said nozzle member at the mouth of the mold, said ring having a thickness tapering toward the tip of the nozzle and partially filling the clearance between the sides of the mold adjacent to the mouth and the sides of the nozzle, and means for supplying a stream of stock to said nozzle.

2. Molding apparatus for hollow pulp articles, comprising a hollow screen mold having an open-' ing or mouth therein, a supply nozzle projecting through said opening into said mold, the end portion of said nozzle within the mold having a bore tapering in diameter toward the orifice thereof and an external diameter greater than that of the adjacent portion of the nozzle, a ring on said nozzle member at the mouth of the mold, said ring having a thickness tapering toward the tip of the nozzle and partially filling the clearance between the sides of the mold adjacent to the mouth and the sides of the nozzle, and means for supplying a stream of stock to said nozzle.

3. Apparatus for molding bottle-shaped paperpulp articles, which comprises a hollow mold lined with a foraminous screen with a body portion, a relatively narrow neck portion and an inward flange to form the lip of the molded article, a. supply pipe for pulp stock extending into the interior of said mold, and a ring on said supply pipe opposite the upper part of said neck portion of the mold, said ring tapering downwardly in thickness so as to deflect ascending stock outwardly against said upper part of the mold.

4. The method of making bottle shaped pulp containers characterized by the introduction of the pulp and compressed air into a correspondingly shaped foraminous mold through the reduced neck portion of the mold and through a conduit having a reduced outlet orifice located within the mold at a point sufiiciently removed from the neck entrance to prevent uneven de-' posit of pulp about the neck relative to the other portions of the mold thus securing a pulp COD-.- tainer having the walls thereof of substantially uniform thickness throughout.

ROY D. HEYMANN. FREDERIC C. CLARK. 

